The present invention relates to epidural leads with inflatable anchoring apparatus.
One type of lead commonly used for pain relief and other medical applications is advanced in to the epidural space next to the spine, so that the dura can be electrically stimulated. The location within the epidural space is critical, for a minor error in placement will result in ineffective stimulation. Placement is commonly made by inserting the lead and providing stimulation through an electrode. When relief is sensed in the desired area, the lead is left to permanently attach.
Many prior art devices provide varying means of anchoring a lead in its position within the epidural space. For example, the Medtronic PISCES-SIGMA.RTM. lead has a generally S-shaped portion which bears against the walls of the epidural space to anchor the lead.
Another successful anchoring device is used in the Medtronic PISCES-SPIREL.TM. lead which has small pliable plank-like tines at a distal end of the electrode for connecting by fibrosis to the walls of the epidural space. Additionally, the lead has a helically coiled section which bears out against the walls for anchoring and also for absorbing longitudinal pressures. This spring absorption of pressure further prevents lead dislodgment.
While these leads provide excellent anchoring apparatus, it is also desirable to urge the electrode toward the dura in order to maximize stimulation efficiency. The closer the electrode can be positioned in the dura, the lower the power requirements of the stimulating system. U.S. Pat. No. 4,285,347 to Hess, issued Aug. 25, 1981 discloses a lead for use in the epidural space which has a spring-like member at its distal end for urging electrode toward the dura. The flattening and extension of such a spring requires complicated insertion techniques.
Many implantable devices have used inflatable balloons for holding the device in a position in the body. U.S. Pat. No. 3,635,223 to Klieman discloses an embolectomy catheter which uses an inflatable portion for expanding angle protrusions to engage in embolus, so that the catheter can be withdrawn while gripping the emobolus. U.S. Pat. No. 3,937,225 to Schramm, issued Feb. 10, 1976 discloses a heart lead in which the electrode is anchored by the use of an expandable balloon. U.S. Pat. No. 4,331,133 to Robinson, issued Jan. 19, 1982 discloses an intra-aortic balloon with a flexible catheter.
U.S. Pat. No. 3,448,739 to Stark et al, issued June 10, 1969 shows a double lumen diagnostic balloon catheter in which an inner tube through the catheter allows fluid to be introduced in the balloon to inflate it.
U.S. Pat. No. 3,836,346 to Tower, issued Sept. 24, 1974, discloses another pacing catheter which employs a balloon for cushioning. A pacing lead with a balloon is also marketed by Siemens-Elema as Model 289 SM.
U.S. Pat. No. 4,198,963 to Barkalow et al, issued Apr. 22, 1980 discloses a heart defibrillator which is part of a cardiopulmonary resusitator. To aid in defibrillation, a catheter is inserted through the esophagus. The catheter has a balloon section which is positioned adjacent the heart. Because of the large relative size of this area, it is possible to have electrodes on the balloon. As the balloon is inflated, the esophagus is blocked to prevent food and gastric juices from escaping. The flexible metal strip electrode on the balloon is urged toward the heart. This patent discloses how a syringe may be used to inflate the balloon.
U.S. Pat. No. 3,326,207 to Egan, issued June 20, 1967, discloses a two-balloon system which is used for EKG testing of a fetus in the womb of a mother. One balloon is positioned adjacent the trunk of the fetus and the other adjacent its head. Multiple electrodes are positioned on the balloon. When the balloons are inflated one electrode from each set is likely to be in contact with the fetus. That one of the multiple electrodes is then chosen for electric sensing.
These many uses of balloons all show the common prior art technique of 360.degree. inflation drawn on a catheter to anchor the catheter and to seal the area between the catheter and the body part. These prior art techniques do not allow the directional use of an inflatable balloon for urging an electrode transversely on a lead used in a narrow body cavity such as the epidural space.